This invention relates to a construction system utilizing prefabricated panels adapted to form a roof, wall, flashing, accessory, tank, container, pool, pond liner, or other construction sections, and in one of its aspects to interlocking, self-cleaning fasteners for use in providing a substantially continuous seal between the panels.
The construction of roofs, walls and other elements by conventional methods is a laborious process usually requiring on-site fabrication and erection of a suitable support structure. In an attempt to improve on conventional construction methods, it has been suggested to utilize panels which are prefabricated at the factory and are secured together at the job site. Co-pending patent applications Ser. No. 336,370, entitled "Roof Construction," and Ser. No. 336,364, entitled "Construction System," both filed on Feb. 27, 1973, and assigned to the assignee of this invention, illustrate highly satisfactory apparatus and methods for providing such improvements.
In patent application Ser. No. 336,364, a composite panel is disclosed as having a structural core which may be conventional laminated foam, cellular honeycomb or concrete, as well as other construction materials. An exterior sheeting or membrane of weathertight material such as a plastic or light gauge metal is secured to the outer surface of the panel. The membrane is formed with a flap along one or several edges which is adapted to overlie a marginal portion of an adjacent panel. The membrane flap is adapted to sealingly engage the marginal portion of the next adjacent panel. In the preferred form of the invention disclosed in that application, the flap and marginal membrane portions are sealable by virtue of male and female interlocking fasteners carried on the respective membrane portions. The interlocking fastener structure may take various forms and may include an expandable section to accommodate field assembly.
In patent application Ser. No. 336,370, a prefabricated panel is disclosed which is ideally suited for roof construction. The panel utilizes a corrugated metal member as a structural core, and an exterior, weather resistant sheet material is pre-adhered to the panel exterior. The sheet msterial is formed with a flap along one or several edges which is adapted to overlie a marginal portion of an adjacent panel. A seal is effected between overlapping membrane members by vulcanization or by virtue of interlocking fasteners carried on the flap and the marginal portions of the next adjacent panel.
In any such system as described with respect to the referenced co-pending patent applications, the fasteners employed for connection to the panels in the field must be easily and quickly operated, and must provide an effective continuous seal such as against weather. However, in the fasteners employed in such systems male and female coupling members of different configurations are generally provided, and it is not uncommon for dirt to get into and along the inside of the coupling members of the fastener, particularly during field use. When such occurs, because of the relatively close fit of the coupling members of the fasteners, dirt is pushed and packed inside the fastener during joining of two fasteners until, in some cases, it is difficult to fully close the fasteners and a leak may occur between them.
In the construction system of the present invention, which is of the same general type as disclosed in the aforementioned co-pending patent applications, this problem is effectively eliminated or substantially reduced by providing a plurality of construction panels, each of which includes a core member, and an exterior sheeting or membrane member formed with a novel fastener disposed along each adjacent edge of the membrane member of adjacent panels for interlocking engagement therebetween. Each such fastener includes means for wiping along the inside walls of another fastener to be connected therewith to wipe away dirt accumulated thereon, and at least one dirt cavity is provided in the fastener for receiving the dirt as it is pushed from the inside walls of the fastener. The respective fasteners that are coupled together include male and female interlocking members and the dirt cavity is formed by making the female portion deeper than the extent of penetration of the male member. As the fasteners are joined, the male member of each fastener wipes down across the inside surface of the mating female members of the other fastener and dislodges dirt or dust on these surfaces to allow a good seal between the fasteners. If this dirt were not removed by this wiping process, it would form a permeable barrier and act as a channel to allow water, air, or other fluid to penetrate the fasteners by flowing through the channel.
In the form of fastener illustrated herein, the fastener is an elongated zipper of flexible material that includes a body portion having male and female coupling means, such as projecting ribs and intermediate grooves for interlocking engagement with an identical zipper on an adjacent panel. The zippers include a connecting web extending from the zipper body which may be bonded to the edge of each membrane member so that the zippers along two opposite edges of the membrane member face inwardly towards the panel, and the zippers along the other two opposite edges of the membrane member extend outwardly from the panel. The zippers can be disposed along their respective membrane member edges so that they slightly extend beyond these edges a sufficient amount so that when adjacent panels are abutting each other adjacent zippers are overlapped for proper engagement. Also, if desired, the membrane members can be provided with opposite flap and marginal portions along their edges as described in patent application Ser. No. 336,364, with the fastener of this invention disposed along each of these portions. Further, the expansion/contraction feature illustrated in that application may be utilized if the fasteners are not overlapped as described.
In designing fasteners of the type utilized in the present invention a difficult problem is to provide adequate sealing between the fasteners. This is particularly true where inclusion of some dirt which is not wiped away occurs, or a manfacturing defect occurs in a section of one of the fasteners.
In the process of manufacturing the fasteners of the present invention, it is more difficult to consistently get two large flat surfaces that mate continuously than it is to have one flat surface and one substantially knife-like edge surface mate continuously. This is especially true since the fasteners of the present invention are generally made of a somewhat flexible material that can deform slightly so that the total amount of pressure will be much more intense (force per unit area) if distributed across a substantially knife-like edge rather than if distributed across two more massive surfaces.
Thus, in order to ensure proper sealing, particularly in the instances noted it is preferred that several areas of intensive contact be formed by substantially line contacts (analogous to a knife edge) between the surfaces of the contacting fasteners instead of extensive contact between flat surfaces. By creating a number of lines of relatively intense contact between the mating surfaces, water can be effectively prevented from passing these contact areas.
It is also desirable, as noted, that the zippers be formed of a material which is sufficiently deformable under pressure to flow into voids in the areas of intensive contact to further aid in providing a watertight seal.
Each of the intense contact areas should be complete, continuous and of enough intensity to prevent the pressure of the water from forcing the surfaces of adjoining fasteners apart and from passing between those two surfaces. Also, by using multiple points of intense contact, even if dirt is not wiped from one area, or a manufacturing defect prevents adequate sealing in one area, other areas of contact will provide sealing.
An important feature of the present invention is that the fasteners employed can be readily designed to include these areas of intense contact. Also, the fasteners can be pre-shaped during manufacture so that they have a tendency to pinch together or close on themselves when mated together to increase the intensity of the contact in the areas of intense contact. A further feature of this invention is the provision of a system and process of manufacturing the fasteners to provide the pre-shaped fastener.
It is preferred that the fasteners of this invention (both the body and web portion) be made of an extruded flexible material, such as Hypalon (as hereinafter defined), which is normally of a thermoplastic state, and that the fastener be extruded in a configuration where its ribs are pinched-in towards each other. The flexible material should be adapted to respond to treatment whereby the body portion can be stiffened and permanently shaped to its extruded configuration by increasing its elastic modulus and permanent set without destroying the thermoplastic properties of the web portion. Following such treatment the ribs of the body portion are resilient and remain normally pinched in towards each other prior to mating with another fastener and have to be forced away from each other during insertion into another fastener. Because of their resilient properties they then pinch towards each other again enough after insertion to increase the sealing pressure with the mated fastener in the areas of intensive contact. This treatment to only the body portion of the fastener also permits it to withstand tension and compressive forces during usage which would otherwise cause it to fail, while permitting the web portion to be bonded to the flexible membrane of a panel, such as by a heat weld, as hereinafter described. In order to so stiffen and permanently shape the body portion of the fastener, without doing so to the web portion, it is preferred that an irradiation process using Beta or equivalent rays be used as hereinafter described in detail for curing and cross-linking the body portion only. As also disclosed herein the extruded fastener material may be irradiated only to the depth of the body portion either while a length of fastener material is coiled together, such as to facilitate packaging and shipping, or while the fastener material is provided in continuous strips moving past a radiation source in a continuous process.
In field use of the fasteners described, where many feet of structural panels may be joined together in a day, even with easily installed fasteners it is not uncommon for a small section of the fastener to be left unfastened, or only partially joined, so that a leak can develop. Even when the installed system is visibly inspected, it is easy to miss seeing the unfastened or only partially joined section or sections since the system is generally a large surface area of the same color.
In the construction system of the present invention, this problem is effectively eliminated by providing fasteners such as described which include at least one indicator means providing a distinctive visual indication when the adjacent fasteners are not fully and properly engaged. Preferably, this means is a stripe having a color different from the color of the remainder of the fastener. The color stripe on each fastener is located along an edge thereof that is exposed except when the fastener is fully engaged with an adjacent fastener so that a person inspecting the system after installation can readily detect sections of the connected fasteners not fully closed. A kick flap may be provided on each fastener or on only one of the fasteners for deflecting forces that would tend to separate the fasteners, and to cover the color stripe when the fasteners are properly fastened. By use of the kick flap, the color stripe can be positioned on the fastener so that it can be easily seen from above the fastener when installed, but not fully connected.
With the use of zippers such as described, it is also possible that they can be improperly engaged in by inserting a rib member in the wrong groove and this condition go unnoticed during visual inspection. Thus, in another embodiment of this invention, an elongated color stripe can also be provided along the length of that portion of any rib member that may be exposed when the ribs and grooves are improperly engaged as described. In this way, even if the color stripe along the edge of the fastener is covered, the second color stripe will be visible during inspection.
Various forms of dust caps may be provided for the fasteners of this invention to further aid in ensuring that the fasteners will seal together in the field despite the fact that they may be stored or used in an environment of dust and dirt. Generally the dust caps can be installed at the factory either before or after the fasteners are bonded to the construction panels, and removed during installation in the field. In usage of the pre-shaped fastener described it is preferred that a dust cap member be provided which projects into the grooves of the body member and causes the ribs thereof to spread open. Thus, when the dust cap is removed upon field installation the fasteners can be easily coupled with a similar fastener as the ribs will not immediately take their pinched configuration. It has been found, however, that in a short period of time the ribs of the fasteners will creep back to their pinched configuration to provide the advantages thereof previously noted.
Thus, by use of the novel zipper design disclosed and claimed herein, a construction system is provided which can be erected and installed efficiently and economically with a good chance that the integrity of the seal provided by the system will be greatly increased because dirt accumulated on the fastener elements will not normally impede proper connection of the fasteners, and areas of intensive contact between the surfaces of joined fasteners will be maintained. Also by use of the visual indicator described there will be good chance that the seal provided by the fasteners will be ensured even with only a casual visual inspection or "walking over" of the system during or after installation.